Apparatus and method for producing two-sided patterned web in registration

ABSTRACT

An apparatus for casting a patterned surface on both sides of an opaque web. The apparatus includes a first patterned roll, a second pattered roll, and a means for rotating the first and second patterned rolls such that their patterns are transferred to opposite sides of the opaque web while it is in continuous motion. During this process, their patterns are maintained in continuous registration to within at least 100 micrometers.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.12/837,826, filed Jul. 16, 2010, now allowed, which is a divisional ofU.S. application Ser. No. 11/370,136, filed Mar. 6, 2006, now U.S. Pat.No. 7,767,273, which claims the benefit of U.S. Provisional ApplicationNo. 60/661,430, filed Mar. 9, 2005, the disclosure of which isincorporated by reference in their entirety herein.

TECHNICAL FIELD

The disclosure relates generally to the continuous casting of materialonto a web, and more specifically to the casting of articles having ahigh degree of registration between the patterns cast on opposite sidesof the web. In particular, the disclosure relates to casting patternsonto opposite sides of a web with a high degree of registration.

BACKGROUND

Many articles can be manufactured by applying a material that is atleast temporarily in liquid form to opposite sides of a substrate. It isoften the case that the material applied to the substrate is applied ina predetermined pattern. It is common in such cases for there to be atleast a minimum requirement for registration between the patterns onopposite sides of the substrate. In some cases, it is necessary for thepatterns on either side of a substrate to be aligned within very smalltolerances.

A need remains, therefore, for improved techniques, apparatus andmethods of producing two-sided substrates in which each side of thesubstrate bears a predetermined pattern in close registration with thepredetermined pattern on the other side of the substrate. A need remainsfor improved techniques, apparatus and methods of reproducing closelyregistered microreplicated patterns on either side of a flexible, atleast partially opaque web or substrate.

SUMMARY

The disclosure pertains generally to improved techniques, apparatus andmethods of reproducing closely registered microreplicated patterns oneither side of a flexible web or substrate.

Accordingly, an illustrative embodiment of the disclosure may be foundin an assembly that includes an energy source adapted to provide curingenergy. The assembly includes a first patterned roll having a number ofregions that are opaque to the curing energy disposed on a substratethat is transparent to the curing energy. The opaque regions define afirst pattern. The assembly includes a second patterned roll that definea second pattern. The second patterned roll can have a number of regionsthat are opaque to the curing energy disposed on a substrate that istransparent to the curing energy, where the opaque regions define asecond pattern.

The assembly also includes means for rotating the first and secondpatterned rolls such that the first and second patterns are maintainedin continuous registration to within 100 micrometers. In some instances,the first and second patterns are maintained in continuous registrationto within 10 micrometers.

In some instances, the opaque regions block, scatter, absorb or reflectat least 98 percent of the curing energy incident upon the opaqueregions. In some cases, the transparent substrates permit at least 25percent of the curing energy incident upon the transparent substrates topass through. In some cases, the substrates define an outer substratesurface, and the opaque regions extend radially outwardly from the outersubstrate surface. In some instances, the opaque regions are located ata periphery of the substrate, and the transparent regions of thesubstrate extend inwardly from the periphery.

Another illustrative embodiment of the disclosure may be found in anapparatus that includes an energy source that is adapted to providecuring energy, a first patterned roll and a second patterned roll. Theenergy source may be adapted to provide ultraviolet light. The firstpatterned roll includes a number of regions that are opaque to thecuring energy disposed on a substrate that is transparent to the curingenergy. The opaque regions define a first raised pattern. The secondpatterned roll includes a number of regions that are opaque to thecuring energy disposed on a substrate that is transparent to the curingenergy. The opaque regions define a second raised pattern.

The apparatus also includes one or more feed rolls that are adapted toprovide a web and to feed the web into contact with the first and secondpatterned rolls. In some embodiments, the web has first and second sidesand can be opaque to the curing energy. A first dispenser is adapted todispose a curable material onto the first side of the web or the firstpatterned roll before the web contacts the first patterned roll and asecond dispenser is adapted to dispose a curable material onto thesecond side of the web or the second patterned roll before the webcontacts the second patterned roll.

The apparatus also includes means for rotating the first and secondpatterned rolls such that the first and second raised patterns areimprinted in the curable material on the first and second sides of theweb while the web is in continuous motion, and the first and secondraised patterns are maintained in continuous registration on the firstand second sides of the web to within 100 micrometers. In someinstances, the first and second raised patterns are maintained incontinuous registration to within 10 micrometers.

In some instances, the opaque regions block, scatter, absorb or reflectat least 98 percent of the curing energy incident upon the opaqueregions. In some cases, the transparent substrates permit at least 10percent of the curing energy incident upon the transparent substrates topass through. In some instances, the web permits less than 2 percent ofcuring energy incident on the web to pass through the web.

In some instances, the transparent substrates may include a glasscylinder and may in particular cases include a quartz cylinder. Thetransparent substrates may be a polymeric cylinder such as a PMMA (polymethyl methacrylate) cylinder. The opaque regions may include materialssuch as chrome, copper, aluminum or epoxy.

The energy source may, in some instances, be adapted to provide curingenergy that passes at least partially through the first patterned rolland/or at least partially through the second patterned roll. The energysource may include a first curing energy source disposed within thefirst patterned roll and a second curing energy source disposed withinthe second patterned roll.

Another illustrative embodiment of the disclosure may be found in amethod of patterning an opaque web that has a first side and a secondside. Curable material is disposed onto the opaque web, which is thendirected into contact with a first patterned roll having a number ofraised opaque regions disposed on a transparent substrate. Ultravioletradiation is directed at least partially through the first patternedroll, thereby curing the curable material on the first side of theopaque web to form a first pattern. The opaque web is then directed intocontact with a second patterned roll having a number of opaque regionsdisposed on a transparent substrate. Ultraviolet radiation is directedat least partially through the second patterned roll, thereby curing thecurable material on the second side of the opaque web to form a secondpattern. The first and second sides of the web are patterned while theweb is in continuous motion such that the first and second patterns aremaintained in continuous registration to within 100 micrometers. In someinstances, the first and second patterns are maintained to within 10micrometers.

In some instances, disposing curable material onto the opaque webincludes disposing curable material onto the first side of the web orfirst patterned roll prior to the first side of the web contacting thefirst patterned roll and disposing curable material onto the second sideof the web or second patterned roll prior to the second side of the webcontacting the second patterned roll.

Another illustrative embodiment of the disclosure may be found in apatterned roll that includes a curing energy transparent cylinder, a tielayer disposed on the curing energy transparent cylinder, and a numberof curing energy opaque features disposed on the tie layer to form apattern. The curing energy transparent cylinder permits at least 10percent of curing energy light incident upon the cylinder to passthrough the cylinder while the curing energy opaque features block atleast 98 percent of curing energy light incident upon the curing energyopaque features. In some particular instances, the curing energytransparent cylinder includes quartz, the tie layer includes titanium,and the curing energy opaque feature includes chrome.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The Figures, Detailed Description and Examples which followmore particularly exemplify these embodiments.

Definitions

In the context of this disclosure, “registration,” means the positioningof structures on one surface of the web in a defined relationship toother structures on the opposite side of the same web.

In the context of this disclosure, “web” means a sheet of materialhaving a fixed dimension in a first direction and either a predeterminedor indeterminate length in a second direction that is orthogonal to thefirst direction.

In the context of this disclosure, “continuous registration,” means thatat all times during rotation of first and second patterned rolls thedegree of registration between structures on the rolls is better than aspecified limit.

In the context of this disclosure, “microreplicated” or“microreplication” means the production of a microstructured surfacethrough a process where the structured surface features retain anindividual feature fidelity during manufacture, from product-to-product,that varies no more than about 100 micrometers.

In the context of this disclosure, “curing energy” refers toelectromagnetic radiation having a particular wavelength or band ofwavelengths suitable for curing a curable material. The phrase “curingenergy” may be modified by a term identifying the wavelength or band ofwavelengths. For example, “ultraviolet curing energy” refers to energywithin a band of wavelengths that is considered to be ultraviolet andthat is suitable for curing a particular material. The phrase “curablematerial”, when used in conjunction with “curing energy”, refers to amaterial that may be cured, polymerized or cross-linked when exposed to“curing energy”.

In the context of this disclosure, “opaque” refers to a material thatblocks at least a significant amount of electromagnetic radiation of aparticular wavelength or band of wavelengths. A material may beconsidered to be opaque to energy of a first wavelength, but not beopaque to energy of a second wavelength. A material that is “opaque” toenergy of a particular wavelength may block at least 95 percent of theenergy of that particular wavelength that is incident upon the material.An “opaque” material may block 98 percent or even more than 99 percentof the energy of that particular wavelength that is incident upon thematerial.

A material may be described as “opaque to curing energy”, meaning thatthe material blocks at least 95 percent of the curing energy (of aparticular wavelength or band of wavelengths) incident upon thematerial. A material described as “opaque to ultraviolet energy” wouldblock at least 95 percent of ultraviolet radiation incident upon thematerial.

A material such as a flexible web or substrate may be described as“opaque”, meaning that the flexible web or substrate blocks at least 95percent of the electromagnetic energy of a particular wavelength or bandof wavelengths incident upon the flexible web or substrate. A flexibleweb or substrate may be described as described as “opaque to curingenergy”, meaning that the flexible web or substrate blocks at least 95percent of the curing energy (of a particular wavelength or band ofwavelengths) incident upon the flexible web or substrate. A flexible webor substrate described as “opaque to ultraviolet energy” would block atleast 95 percent of ultraviolet radiation incident upon the flexible webor substrate.

As used within the context of this disclosure, “transparent” refers to amaterial that transmits, or permits passage, of at least a significantamount of electromagnetic radiation of a particular wavelength or bandof wavelengths. A material may be considered to be transparent to energyof a first wavelength, but not be transparent to energy of a secondwavelength. A material that is “transparent” to energy of a particularwavelength may transmit or permit passage at least 10 percent of theenergy of that particular wavelength that is incident upon the material.A “transparent” material may transmit or permit passage of 25 percent oreven more than 50 percent of the energy of that particular wavelengththat is incident upon the material.

A material may be described as “transparent to curing energy”, meaningthat the material transmits or permits passage of at least 10 percent ofthe curing energy (of a particular wavelength or band of wavelengths)incident upon the material. A material described as “transparent toultraviolet energy” would transmit or permit passage of at least 10percent of ultraviolet radiation incident upon the material.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a casting apparatus in accordancewith an embodiment of the disclosure;

FIG. 2 is a schematic illustration of a portion of the casting apparatusshown in FIG. 1;

FIG. 3 is a partial illustration of a patterned roll in accordance withan embodiment of the disclosure;

FIGS. 4-13 demonstrate an illustrative but non-limiting method offorming the patterned roll of FIG. 3 in accordance with an embodiment ofthe disclosure;

FIGS. 14A-14E demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIGS. 15A-15D demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIGS. 16A-16D demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIGS. 17A-17C demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIGS. 18A-18C demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIGS. 19A-19D demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIGS. 20A-20E demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIGS. 21A-21D demonstrate an illustrative but non-limiting method offorming a patterned roll in accordance with an embodiment of thedisclosure;

FIG. 22 is a perspective view of a microreplication assembly inaccordance with an embodiment of the disclosure;

FIG. 23 is a perspective view of a portion of the microreplicationassembly of FIG. 22;

FIG. 24 is a perspective view of a portion of the microreplicationassembly of FIG. 22;

FIG. 25 is a schematic illustration of a roll mounting arrangement inaccordance with an embodiment of the disclosure;

FIG. 26 is a schematic illustration of a mounting arrangement for a pairof patterned roll in accordance with an embodiment of the disclosure;

FIG. 27 is a schematic illustration of a motor and roll arrangement inaccordance with an embodiment of the disclosure;

FIG. 28 is a schematic illustration of structure for controlling theregistration between rolls in accordance with an embodiment of thedisclosure;

FIG. 29 is a schematic illustration of a control algorithm forcontrolling registration in accordance with an embodiment of thedisclosure; and

FIG. 30 is a diagrammatic cross-sectional view of an article made inaccordance with an embodiment of the disclosure;

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the disclosureto the particular embodiments described. On the contrary, the intentionis to cover all modifications, equivalents, and alternatives fallingwithin the spirit and scope of the disclosure.

DETAILED DESCRIPTION

Generally, the present disclosure pertains to producing two-sidedmicroreplicated structures having a first microreplicated pattern on afirst surface of a web and a second microreplicated pattern on a secondsurface of the web. The system generally includes a first patterningassembly and a second patterning assembly. Each respective assemblycreates a microreplicated pattern on either a first or second surface ofthe web. A first pattern can be created on the first surface of the weband a second pattern can be created on the second surface of the web.

In some instances, the apparatus and methods discussed herein result ina web having a microreplicated structure on each opposing surface of theweb that can be manufactured by continuously forming microreplicatedstructures on opposite surfaces of the web while keeping themicroreplicated structures registered generally to within 100micrometers of each other. In some instances, the microreplicatedstructures may remain registered within 50 micrometers. In some cases,the microreplicated structures may remain registered within 20micrometers. In some instances, the microreplicated structures mayremain registered within 10 micrometers or even within 5 micrometers.

The following description should be read with reference to the drawings,in which like elements in different drawings are numbered in likefashion. The drawings, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of thedisclosure. Although examples of construction, dimensions, and materialsare illustrated for the various elements, those skilled in the art willrecognize that many of the examples provided have suitable alternativesthat may be utilized.

Casting Assembly

FIG. 1 illustrates an example casting apparatus 10 for producing atwo-sided web 12 that includes registered microreplicated structures onopposing surfaces. In some instances, the casting apparatus 10 includesfirst and second coating means 16, 20, a nip roller 14, and first andsecond patterned rolls 18, 24. In some instances, first coating means 16may be a first extrusion die 16 while second coating means may be asecond extrusion die 20. In the illustrated embodiment, the first andsecond curable liquid is disposed on the web surface prior to passingthrough the first and second patterned rolls, respectively. In otherembodiments, the first curable liquid is disposed on the first patternedroll and the second curable liquid is disposed on the second patternedroll, which is then transferred to the web from the patterned rolls.

Web 12 may be presented to the first extrusion die 16, which dispenses afirst curable liquid layer coating 22 onto the web 12. Nip roller 14presses first coating 22 into the first patterned roller 18. In somecases, nip roller 14 can be a rubber covered roller. While on the firstpatterned roll 18, the coating 22 is cured using an energy source 26adapted to provide suitable curing energy. In some instances, energysource 26 may be adapted to provide ultraviolet light. The term“ultraviolet light” refers to light having a wavelength in a range from200 to 500 nanometers or from 200 to 400 nanometers.

A second curable liquid layer 28 is coated on the opposite side of theweb 12 using a second side extrusion die 20. The second layer 28 ispressed into the second patterned tool roller 24 and the curing processrepeated for the second coating layer 28. Registration of the twocoating patterns is achieved by maintaining the tool rollers 18, 24 in aprecise angular relationship with one another, as will be describedhereinafter.

FIG. 2 provides a closer view at first and second patterned rolls 44 and46. First and second patterned rolls 44, 46 may be considered asparticular embodiments of patterned rolls 18, 24 as discussed withrespect to FIG. 1. Other patterns are contemplated, as will be discussedin greater detail subsequently. First patterned roll 44 has a firstpattern 42 for forming a microreplicated surface. Second pattern roll 46has a second microreplicated pattern 50. In the illustrated embodiment,first and second patterns 42, 50 are the same pattern. In otherinstances, the first and second patterns may be different.

As a web 30 passes over the first patterned roll 44, a first curableliquid (not shown) on a first surface 32 may be cured by curing energyprovided by an energy source 34 near a first region 36 on the firstpatterned roll 44. A first microreplicated patterned structure 54 isformed on the first side 43 of the web 30 after the liquid is cured. Thefirst patterned structure 54 is a negative of the pattern 42 on thefirst patterned roll 44. After the first patterned structure 54 isformed, a second curable liquid 52 is dispensed onto a second surface 38of the web 30. To insure that the second liquid 52 is not curedprematurely, the second liquid 52 is isolated from the first energysource 34, typically by locating the first energy source 34 so thatenergy emitted by the first energy source 34 does not fall on the secondliquid 52. If desired, the curing sources can be located inside theirrespective patterned rolls. As such, the opaque nature of web 30 can aidin preventing undesired curing.

After the first patterned structure 54 is formed, the web 30 continuesalong the first roll 44 until it enters a gap region 48 between thefirst and second patterned rolls 44, 46. The second liquid 52 thenengages the second pattern 50 on the second patterned roll 46 and isshaped into a second microreplicated structure, which is then cured bycuring energy emitted by a second energy source 40. As the web 30 passesinto the gap 48 between first and second patterned rolls 44, 46, thefirst patterned structured 54, which is by this time substantially curedand bonded to the web 30, restrains the web 30 from slipping while theweb 30 begins moving into the gap 48 and around the second patternedroller 46. This removes web stretching and slippages as a source ofregistration error between the first and second patterned structuresformed on the web.

By supporting the web 30 on the first patterned roll 44 while the secondliquid 52 comes into contact with the second patterned roll 46, thedegree of registration between the first and second microreplicatedstructures 54, 56 formed on opposite sides 32, 38 of the web 30 becomesa function of controlling the positional relationship between thesurfaces of the first and second patterned rolls 44, 46. The S-wrap ofthe web around the first and second patterned rolls 44, 46 and betweenthe gap 48 formed by the rolls minimizes effects of tension, web strainchanges, temperature, microslip caused by mechanics of nipping a web,and lateral position control. The S-wrap can maintain the web 30 incontact with each roll over a wrap angle of 180 degrees, though the wrapangle can be more or less depending on the particular requirements.

Patterned Roll

In some instances, it may be useful to provide microreplicated patternsonto either side of a flexible web or substrate that is opaque,particularly, opaque to curing energy. In other instances, it may beuseful to provide microreplicated patterns onto either side of aflexible web or substrate that is transparent, particularly, transparentto curing energy. When the web or substrate is opaque to the curingenergy necessary to cure the materials applied to the web in liquidform, the materials cannot simply be cured by passing curing energythrough the web or substrate to contact the liquid resin. In thesecases, it may be useful to use a patterned roll that is transparent to aparticular curing energy or includes portions that are transparent tocuring energy. In some cases, only one patterned roll is transparent.

FIG. 3 is a partial illustration of an illustrative but non-limitingpatterned roll and should not be considered as being to scale. Instead,the pattern has been exaggerated for clarity. Patterned roll can, asillustrated and as will be discussed in greater detail, may be formed byan additive method in which materials are deposited onto the surface ofa transparent cylinder or other suitable shape. In some embodiments, itis believed that patterned roll may be formed using various subtractivemethods in which material is removed from a transparent cylinder orother suitable shape.

Patterned roll includes a transparent cylinder 102 that can be formed ofany suitable material. In some instances, transparent cylinder 102 isformed of a material that is transparent to the curing energy that willcure the curable material that will be applied to patterned roll. Insome instances, as illustrated, transparent cylinder 102 can be madefrom a glass such as quartz.

As illustrated, in particular, patterned roll includes a quartz cylinder102. Quartz cylinder 102 may be of any suitable dimensions, although insome cases quartz cylinder 102 may have a length of 3 inches and aradius of 3 inches. Quartz cylinder 102 may be a substantially solidcylinder, or, as illustrated, quartz cylinder 102 may be a hollowcylinder.

In some cases, it may be useful to apply a thin tie layer 104 to thesurface of the quartz cylinder 102. This may assist subsequent materialsin adhering or bonding to the quartz. In some instances, tie layer 104is thin enough to not materially change the optical properties of thequartz cylinder 102. At a minimum, tie layer 104 can be thin enough toremain transparent to curing energy. Tie layer 104 may be formed of anysuitable material and using any suitable application technique. In someinstances, tie layer 104 includes or consists of titanium and is appliedvia sputtering.

Once tie layer 104 has been formed, subsequent materials may be added topatterned roll. While particular processing steps are illustrated inFIGS. 4-13, and will be discussed in detail with respect to the Example,a variety of opaque materials may be applied to tie layer 104. Suitableopaque materials include metals such as chrome, copper or aluminum, andcurable polymers such as silicone and epoxy. Suitable materials may beapplied and patterned using any suitable technique, such as sputtering,etching, and the like.

In the illustrated embodiment, the features of patterned roll have beenformed in two steps. First, layers 106 have been deposited onto tielayer 104 and subsequently patterned. Layers 108 have been formed andpatterned on top of layers 106. Layers 106 and layers 108 may be formedof different materials or they may be formed of the same material. Insome instances, layers 106 may be formed by sputtering a layer of chromeonto tie layer 104. In some instances, layers 108 may be formed byplating chrome onto layers 106.

In FIG. 3, the opaque features of patterned roll stand above the surfaceof quartz cylinder 102. In some contemplated embodiments, such as thosediscussed with respect to FIGS. 14-21, the opaque features are actuallycloser to an outer surface of the substrate, while the transparentfeatures actually penetrate the substrate. In either event, the opaquefeatures may be considered as being farther from a radial center ofpatterned roll than are the transparent features.

In some instances, a patterned roll may be formed from either machinableor non-machinable transparent substrates. Several contemplatedmanufacturing techniques are described herein in FIGS. 14-21. It shouldbe noted that in FIGS. 14-21, only a very small part of a transparentsubstrate is shown, for ease of illustration. While only a singletransparent feature is shown for each potential manufacturing technique,it should be noted that of course a patterned roll will include a numberof features. Moreover, it should be noted that a patterned roll will becylindrical, while for ease of illustration and because only a verysmall part of the roll is shown, FIGS. 14-21 appear rectangular.

FIGS. 14A-14E illustrate a potential method of forming opaque featureson a non-machinable transparent substrate that includes adding amachinable layer. In FIG. 14A, a non-machinable, transparent, substrate200 is provided. Examples of non-machinable, transparent substratesinclude glasses such as quartz. As shown in FIG. 14B, a titanium tielayer 202 may be applied to substrate 200 using any suitable techniquesuch as sputtering. A copper seed layer 204 may be sputtered ontotitanium tie layer 202 as seen in FIG. 14C. Additional copper may beplated onto copper seed layer 204 to form copper layer 206, as seen inFIG. 14D.

FIG. 14E shows that copper layer 206 could be machined in any suitablemanner to provide a transparent feature 208 positioned within copperlayer 206, which is of course opaque. In some instances, transparentfeature 208 could be formed simply by a machining process such asmicromilling, laser ablation, diamond turning or EDM processing. In somecases, additional processing such as a brief chemical etch may be usefulin exposing transparent substrate 200 without damaging transparentsubstrate 200.

In some instances, other materials may be used for the machinable layer206. For example, machinable layer 206 could be formed from an opaqueepoxy or a machinable ceramic that could be coated in a “green” stateand sintered after shaping.

FIGS. 15A-15D illustrate another potential method of forming opaquefeatures on a non-machinable transparent substrate 200 that includesadding a machinable layer. In FIG. 15B, a transparent epoxy layer 210may be added to the transparent substrate 200 to help protect thetransparent substrate during subsequent machining As seen in FIG. 15C,an opaque epoxy layer 212 has been added on top of the transparent epoxylayer 210. In FIG. 15D, opaque epoxy layer 212 has been machined usingany suitable technique to form transparent feature 214.

FIGS. 16A-D illustrate another potential method of forming opaquefeatures on a non-machinable transparent substrate 200 that includesadding a machinable layer. Transparent substrate 200 is shown in FIG.16A. In FIG. 16B, a relatively thicker transparent epoxy layer 210 hasbeen added atop transparent substrate 200. A relatively thinner opaqueepoxy layer 212 has been added on transparent epoxy layer 210 as shownin FIG. 16C. In FIG. 16D, the opaque epoxy layer 212 and the transparentepoxy layer 210 have been machined using any suitable technique to formtransparent feature 216. As an alternate, it may be feasible to machinetransparent feature 216 into a transparent epoxy layer, then coat thetops of the transparent epoxy layer with an opaque epoxy layer.

FIGS. 17A-17C illustrate a potential method of forming opaque featureson a machinable transparent substrate. FIG. 17A shows a machinabletransparent substrate 220 that can be formed of a machinable transparentpolymer. In some instances, substrate 220 can be formed from PMMA (polymethyl methacrylate). In FIG. 17B, an opaque coating 222 such assputtered aluminum or copper has been added onto transparent substrate220. Alternatively, it is contemplated that opaque coating 222 couldalso be formed from an opaque epoxy or even an opaque filled epoxy. Asshown in FIG. 17C, a transparent feature 224 can be formed using anysuitable machining technique.

FIGS. 18A-C illustrate another potential method of forming opaquefeatures on machinable transparent substrate 220. In FIG. 18B,transparent substrate 220 has been machined using any suitable techniqueto form transparent feature 226. Subsequently, as shown in FIG. 18C, theportions of transparent substrate 220 beyond transparent feature 226 maybe coated with an opaque coating 228.

FIGS. 19A-19D illustrate a potential method of using aseparately-created master mold to replicate raised features on atransparent substrate. The raised features can then be coated to beopaque. In FIG. 19A, a master mold 230 can be cut from any suitablematerial using standard precision machining techniques. Master mold 230can be seen to include protrusion 232, which will ultimately form atransparent feature.

As seen in FIG. 19B, master mold 230 can be filled with an opaque epoxymaterial 234 and then is applied to the surface of a desired substrate236 such as quartz or PMMA as seen in FIG. 19C. The epoxy can be allowedto cure, and then master mold 230 may be removed, as seen in FIG. 19D,leaving substrate 236 having a transparent feature 238 with an opaquelayer 234 on either side of the transparent feature 238.

FIGS. 20A-20E illustrate another potential method of using aseparately-created master mold to replicate raised features on atransparent substrate. The raised features can then be coated to beopaque. In FIG. 20A, a master mold 240 can be cut from any suitablematerial using standard precision machining techniques. Master mold 240can be seen to include protrusion 242, which will ultimately form atransparent feature.

As seen in FIG. 20B, master mold 240 can be filled with a transparentepoxy material 244 and then is applied to the surface of a desiredsubstrate 246 such as quartz or PMMA as seen in FIG. 20C. The epoxy canbe allowed to cure, and then master mold 240 may be removed, as seen inFIG. 20D, leaving substrate 246 having a transparent feature 248. Asseen in FIG. 20E, an opaque epoxy layer 250 can be applied totransparent epoxy layer 244 on either side of the transparent feature248.

FIGS. 21A-21D illustrate another potential method of using aseparately-created master mold to replicate raised features on atransparent substrate. The raised features can then be coated to beopaque. In FIG. 21A, a master mold 252 can be cut from any suitablematerial using standard precision machining techniques. Master mold 252can be seen to include protrusion 254, which will ultimately form atransparent feature.

As seen in FIG. 21B, master mold 252 has been imprinted directly into amachinable transparent substrate 256. In FIG. 21C, master mold 252 hasbeen removed, leaving transparent substrate 256 including transparentfeature 258. As shown in FIG. 21D, transparent substrate 256 can becoated with an opaque epoxy layer 258 on either side of transparentfeature 258.

Casting Apparatus

Referring now to FIGS. 22-23, an example embodiment of a system 110including a roll to roll casting apparatus 120 is illustrated. In thedepicted casting apparatus 120, a web 122 is provided to the castingapparatus 120 from a main unwind spool (not shown). The exact nature ofweb 122 can vary widely, depending on the product being produced.However, the casting apparatus 120 is capable of handling a web 122 thatis both flexible and transparent and/or opaque, as discussed previously.The web 122 is directed around various rollers 126 into the castingapparatus 120.

Accurate tension control of the web 122 is beneficial in achievingoptimal results, so the web 122 may be directed over a tension-sensingdevice (not illustrated). If an optional liner web is used to protectthe web 122, the liner web (not illustrated) can be separated at theunwind spool and directed onto a liner web wind-up spool (not shown).The web 122 can be directed via an idler roll to a dancer roller forprecision tension control. Idler rollers can direct the web 122 to aposition between nip roller 154 and first coating head 156.

A variety of coating methods may be employed. In some embodiments, asillustrated, first coating head 156 is a die coating head. The web 122then passes between the nip roll 154 and first patterned roll 160. Thefirst patterned roll 160 has a patterned surface 162, and when the web122 passes between the nip roller 154 and the first patterned roll 160the material dispensed onto the web 122 by the first coating head 156 isshaped into a negative of patterned surface 162.

While the web 122 is in contact with the first patterned roll 160,material is dispensed from second coating head 164 onto the othersurface of web 122. In parallel with the discussion above with respectto the first coating head 156, the second coating head 164 is also a diecoating arrangement including a second extruder (not shown) and a secondcoating die (not shown). In some embodiments, the material dispensed bythe first coating head 156 is a composition including a polymerprecursor and intended to be cured to solid polymer with the applicationof curing energy such as ultraviolet radiation.

Material that has been dispensed onto web 122 by the second coating head164 is then brought into contact with second patterned roll 174 with asecond patterned surface 176. In parallel with the discussion above, insome embodiments, the material dispensed by the second coating head 164is a composition including a polymer precursor and intended to be curedto solid polymer with the application of curing energy such asultraviolet radiation.

At this point, the web 122 has had a pattern applied to both sides. Apeel roll 182 may be present to assist in removal of the web 122 fromsecond patterned roll 174. In some instances, the web tension into andout of the casting apparatus is nearly constant.

The web 122 having a two-sided microreplicated pattern is then directedto a wind-up spool (not shown) via various idler rolls. If an interleavefilm is desired to protect web 122, it may be provided from a secondaryunwind spool (not shown) and the web and interleave film are woundtogether on the wind-up spool at an appropriate tension.

Referring to FIGS. 22-24, first and second patterned rolls are coupledto first and second motor assemblies 210, 220, respectively. Support forthe motor assemblies 210, 220 is accomplished by mounting assemblies toa frame 230, either directly or indirectly. The motor assemblies 210,220 are coupled to the frame using precision mounting arrangements. Inthe illustrated embodiment, for example, first motor assembly 210 isfixedly mounted to frame 230. Second motor assembly 220, which is placedinto position when web 122 is threaded through the casting apparatus120, may need to be positioned repeatedly and therefore can be movable,both in the cross- and machine direction. Movable motor arrangement 220may be coupled to linear slides 222 to assist in repeated accuratepositioning, for example, when switching between patterns on the rolls.Second motor arrangement 220 also includes a second mounting arrangement225 on the backside of the frame 230 for positioning the secondpatterned roll 174 side-to-side relative to the first patterned roll160. In some cases, second mounting arrangement 225 includes linearslides 223 allowing accurate positioning in the cross machinedirections.

Referring to FIG. 25, a motor mounting arrangement is illustrated. Amotor 633 for driving a tool or patterned roll 662 is mounted to themachine frame 650 and connected through a coupling 640 to a rotatingshaft 601 of the patterned roller 662. The motor 633 is coupled to aprimary encoder 630. A secondary encoder 651 is coupled to the tool toprovide precise angular registration control of the patterned roll 662.Primary 630 and secondary 651 encoders cooperate to provide control ofthe patterned roll 662 to keep it in registration with a secondpatterned roll, as will be described further hereinafter.

Reduction or elimination of shaft resonance is important as this is asource of registration error allowing pattern position control withinthe specified limits. Using a coupling 640 between the motor 633 andshaft 650 that is larger than general sizing schedules specify will alsoreduce shaft resonance caused by more flexible couplings. Bearingassemblies 660 are located in various locations to provide rotationalsupport for the motor arrangement.

In the example embodiment shown, the tool roller 662 diameter can besmaller than its motor 633 diameter. To accommodate this arrangement,tool rollers may be installed in pairs, arranged in mirror image. InFIG. 26, two tool roller assemblies 610, 710 are installed as mirrorimages in order to be able to bring the two tool rollers 662, 762together. Referring also to FIG. 22, the first motor arrangement istypically fixedly attached to the frame and the second motor arrangementis positioned using movable optical quality linear slides.

Tool roller assembly 710 is quite similar to tool roller assembly 610,and includes a motor 733 for driving a tool or patterned roll 762 ismounted to the machine frame 750 and connected through a coupling 740 toa rotating shaft 701 of the patterned roller 762. The motor 733 iscoupled to a primary encoder 730. A secondary encoder 751 is coupled tothe tool to provide precise angular registration control of thepatterned roll 762. Primary 730 and secondary 751 encoders cooperate toprovide control of the patterned roll 762 to keep it in registrationwith a second patterned roll, as will be described further hereinafter.

Reduction or elimination of shaft resonance is important as this is asource of registration error allowing pattern position control withinthe specified limits. Using a coupling 740 between the motor 733 andshaft 750 that is larger than general sizing schedules specify will alsoreduce shaft resonance caused by more flexible couplings. Bearingassemblies 760 are located in various locations to provide rotationalsupport for the motor arrangement.

Because the features sizes on the microreplicated structures on bothsurfaces of a web are desired to be within fine registration of oneanother, the patterned rolls should be controlled with a high degree ofprecision. Cross-web registration within the limits described herein canbe accomplished by applying the techniques used in controllingmachine-direction registration, as described hereinafter.

For example, to achieve about 10 micrometers end-to-end featureplacement on a 10-inch circumference patterned roller, each roller mustbe maintained within a rotational accuracy of ±32 arc-seconds perrevolution. Control of registration becomes more difficult as the speedthe web travels through the system is increased.

Applicants have built and demonstrated a system having 10-inch circularpatterned rolls that can create a web having patterned features onopposite surfaces of the web that are registered to within 2.5micrometers. Upon reading this disclosure and applying the principlestaught herein, one of ordinary skill in the art will appreciate how toaccomplish the degree of registration for other microreplicatedsurfaces.

Referring to FIG. 27, a schematic of a motor arrangement 800 isillustrated. Motor arrangement 800 includes a motor 810 including aprimary encoder 830 and a drive shaft 820. Drive shaft 820 is coupled toa driven shaft 840 of patterned roll 860 through a coupling 825. Asecondary, or load, encoder 850 is coupled to the driven shaft 840.Using two encoders in the motor arrangement described allows theposition of the patterned roll to be measured more accurately bylocating the measuring device (encoder) 850 near the patterned roll 860,thus reducing or eliminating effects of torque disturbances when themotor arrangement 800 is operating.

Apparatus Control

Referring to FIG. 28, a schematic of the motor arrangement of FIG. 27,is illustrated as attached to control components. In the exampleapparatus shown in FIGS. 1-3, a similar set-up would control each motorarrangement 210 and 220. Accordingly, motor arrangement 900 includes amotor 910 including a primary encoder 930 and a drive shaft 920. Driveshaft 920 is coupled to a driven shaft 940 of patterned roll 960 througha coupling 930. A secondary, or load, encoder 950 is coupled to thedriven shaft 940.

Motor arrangement 900 communicates with a control arrangement 965 toallow precision control of the patterned roll 960. Control arrangement965 includes a drive module 966 and a program module 975. The programmodule 975 communicates with the drive module 966 via a line 977, forexample, a SERCOS fiber network. The program module 975 is used to inputparameters, such as set points, to the drive module 966. Drive module966 receives input 480 volt, 3-phase power 915, rectifies it to DC, anddistributes it via a power connection 973 to control the motor 910.Motor encoder 912 feeds a position signal to control module 966 via line972. The secondary encoder 950 on the patterned roll 960 also feeds aposition signal back to the drive module 966 via to line 971. The drivemodule 966 uses the encoder signals to precisely position the patternedroll 960. The control design to achieve the degree of registration isdescribed in detail below.

In the illustrative embodiments shown, each patterned roll is controlledby a dedicated control arrangement. Dedicated control arrangementscooperate to control the registration between first and second patternedrolls. Each drive module communicates with and controls its respectivemotor assembly.

The control arrangement in the system built and demonstrated byApplicants include the following. To drive each of the patterned rolls,a high performance, low cogging torque motor with a high-resolution sineencoder feedback (512 sine cycles×4096 drive interpolation>>2 millionparts per revolution) was used, model MHD090B-035-NG0-UN, available fromBosch-Rexroth (Indramat). Also the system included synchronous motors,model MHD090B-035-NG0-UN, available from Bosch-Rexroth (Indramat), butother types, such as induction motors could also be used.

Each motor was directly coupled (without gearbox or mechanicalreduction) through an extremely stiff bellows coupling, model BK5-300,available from R/W Corporation. Alternate coupling designs could beused, but bellows style generally combines stiffness while providinghigh rotational accuracy. Each coupling was sized so that asubstantially larger coupling was selected than what the typicalmanufacturers specifications would recommend.

Additionally, zero backlash collets or compressive style locking hubsbetween coupling and shafts are preferred. Each roller shaft wasattached to an encoder through a hollow shaft load side encoder, modelRON255C, available from Heidenhain Corp., Schaumburg, Ill. Encoderselection should have the highest accuracy and resolution possible,typically greater than 32 arc-sec accuracy. Applicants' design, 18000sine cycles per revolution were employed, which in conjunction with the4096 bit resolution drive interpolation resulted in excess of 50 millionparts per revolution resolution giving a resolution substantially higherthan accuracy. The load side encoder had an accuracy of +/−2 arc-sec;maximum deviation in the delivered units was less than +/−1 arc-sec.

In some instances, each shaft may be designed to be as large a diameteras possible and as short as possible to maximize stiffness, resulting inthe highest possible resonant frequency. Precision alignment of allrotational components is desired to ensure minimum registration errordue to this source of registration error.

Referring to FIG. 29, identical position reference commands werepresented to each axis simultaneously through a SERCOS fiber network ata 2 ms update rate. Each axis interpolates the position reference with acubic spline, at the position loop update rate of 250 microsecondintervals. The interpolation method is not critical, as the constantvelocity results in a simple constant times time interval path. Theresolution is critical to eliminate any round off or numericalrepresentation errors. Axis rollover is also addressed. In some cases,it is important that each axis' control cycle is synchronized at thecurrent loop execution rate (62 microsecond intervals).

The top path 1151 is the feed forward section of control. The controlstrategy includes a position loop 1110, a velocity loop 1120, and acurrent loop 1130. The position reference 1111 is differentiated, onceto generate the velocity feed forward terms 1152 and a second time togenerate the acceleration feed forward term 1155. The feed forward path1151 helps performance during line speed changes and dynamic correction.

The position command 1111 is subtracted from current position 1114,generating an error signal 1116. The error 1116 is applied to aproportional controller 1115, generating the velocity command reference1117. The velocity feedback 1167 is subtracted from the command 1117 togenerate the velocity error signal 1123, which is then applied to a PIDcontroller. The velocity feedback 1167 is generated by differentiatingthe motor encoder position signal 1126. Due to differentiation andnumerical resolution limits, a low pass Butterworth filter 1124 isapplied to remove high frequency noise components from the error signal1123. A narrow stop band (notch) filter 1129 is applied at the center ofthe motor—roller resonant frequency. This allows substantially highergains to be applied to the velocity controller 1120. Increasedresolution of the motor encoder also would improve performance. Theexact location of the filters in the control diagram is not critical;either the forward or reverse path are acceptable, although tuningparameters are dependent on the location.

A PID controller could also be used in the position loop, but theadditional phase lag of the integrator makes stabilization moredifficult. The current loop is a traditional PI controller; gains areestablished by the motor parameters. The highest bandwidth current looppossible will allow optimum performance. Also, minimum torque ripple isdesired.

Minimization of external disturbances is important to obtain maximumregistration. This includes motor construction and current loopcommutation as previously discussed, but minimizing mechanicaldisturbances is also important. Examples include extremely smoothtension control in entering and exiting web span, uniform bearing andseal drag, minimizing tension upsets from web peel off from the roller,uniform rubber nip roller. In the current design, a third axis geared tothe tool rolls is provided as a pull roll to assist in removing thecured structure from the tool.

Web Material

The web material can be any suitable material on which a microreplicatedpatterned structure can be created. A number of different materials maybe used, depending on the ultimate use of the microreplicated patternedstructure. If, for example, the microreplicated patterned structure willform a flexible circuit board, the web material may be a metallizedpolymeric film such as metallized KAPTON.

Coating Material

The liquid from which the microreplicated structures are created can bea curable photocurable material, such as acrylates curable by UV light.One of ordinary skill in the art will appreciate that other coatingmaterials can be used, for example, polymerizable material, andselection of a material will depend on the particular characteristicsdesired for the microreplicated structures. For example, if a flexiblecircuit board is being made, the coating material may include aconductive or insulating polymer. In some embodiments, the coatingmaterial includes an electroplate masking material and/or nonconductiveor insulating polymers.

Examples of coating means that useful for delivering and controllingliquid to the web or patterned roll are, for example, die or knifecoating, coupled with any suitable pump such as a syringe or peristalticpump. One of ordinary skill in the art will appreciate that othercoating means can be used, and selection of a particular means willdepend on the particular characteristics of the liquid to be deliveredto the web or patterned roll.

Examples of curing energy sources are infrared radiation, ultravioletradiation, visible light radiation, or microwave. One of ordinary skillin the art will appreciate that other curing sources can be used, andselection of a particular web material/curing source combination willdepend on the particular article (having microreplicated structures inregistration) to be created.

Microreplicated Article

FIG. 30 schematically illustrates a contemplated coated microreplicatedarticle 1200 formed according to the methods and using the apparatusdescribed herein. Article 1200 includes a flexible opaque web 1202 and anumber of schematic elements disposed on either side of opaque web 1202.Element 1204 is disposed opposite element 1206. Similarly, element 1208,element 1212 and element 1216 are disposed opposite element 1210,element 1214 and element 1218, respectively. It should be noted thatthese elements can be considered as generically representing a number ofdifferent potential elements. These elements may be circuitry, forexample. In some embodiments, the microreplicated pattern includes anelectroplate mask that can pass through an additive circuit platingstep.

In some embodiments, such as that illustrated, there may be little or nolands between adjacent elements. For example, there may be little or nocoated material remaining on opaque web 1202 between element 1204 andelement 1208. This may have advantages if, for example, the coatedmaterial is an electrically conductive material or an electroplate mask.In some embodiments, an additional washing step can remove uncuredmaterial from the microreplicated pattern to produce a microreplicatedfeatures having no land areas and separated from one another. In otherinstances, article 1202 may include lands, i.e. coated materialremaining on opaque web 1202 between adjacent elements.

EXAMPLE

FIGS. 4-13 illustrate an additive process for forming a patterned rollmuch like patterned roll of FIG. 3. Quartz tubes 3 inches long and 3inches in radius were cleaned with water, acetone and methyl ethylketone (MEK), and were then placed under a UV lamp for 15 minutes. Thequartz tubes were then mounted on a rotating table in a high vacuumsputter chamber, and the pressure within the chamber was slowly reducedto 1×10⁻⁶ Torr over a period of one hour. A strip of chrome plated steelpreviously mounted within the chamber was electrically connected to anarc welder. The arc welder passed a current through the metal strip andthe metal strip was thus heated to red hot. The rotating quartz tubeswere washed by the resulting IR radiation for 10 minutes.

Once the quartz tubes were cleaned, a quartz cylinder 102 as seen inFIG. 4 was sputtered with a thin layer 104 of chrome, which acts as anadhesion layer between the quartz and the nickel layer to follow.

Next, and as shown schematically in FIG. 5, a nickel metallization layer110 was sputtered onto the chrome tie layer 104.

Next, and as shown schematically in FIG. 6, a protective copper layer112 was applied over the nickel metallization layer 110. The copperlayer 112 was a sacrificial layer that was intended to protect thenickel layer 110 from contamination and oxidation during subsequentprocessing steps.

Next, and as shown schematically in FIG. 7, a photoresist (SC Resists,Arch Semiconductor Photopolymers Company) layer 114 has been added ontop of the copper layer 112. The height of the photoresist layer 114ultimately sets the height of the features being formed on quartzcylinder 102. In the Example, the photoresist layer 114 was formed to be50 micrometers thick, and was softbaked at 115 degrees Celsius for 30seconds prior to exposure.

Next, and as shown schematically in FIG. 8, the photoresist layer 114was patterned by shining light in a desired pattern onto the photoresistlayer 114. Consequently, the photoresist layer 114 now has portions 116that will remain, and portions 118 that will be removed afterdeveloping.

Next, and as shown schematically in FIG. 9, the photoresist wasdeveloped. After sitting for at least 30 minutes, the photoresist wassubjected to a post exposure bake at 115 degrees Celsius for 1 minute.The photoresist was then developed via exposure to developing solutionfor 30 to 60 seconds. Consequently, resist portions 116 remain on copperlayer 112 while resist portions 118 have been removed.

Next, and as shown schematically in FIG. 10, the exposed portions ofcopper layer 112 were removed in an etching process. Sodium persulfatewas used to remove the exposed copper because sodium persulfate reactsquickly with copper but slowly with the chrome underlying the copper, asit is desirable to keep the chrome layer as thick as possible.

Next, and as shown schematically in FIG. 11, chrome sections 120 wereplated onto the freshly exposed chrome layer 110, in between resistregions 116. Chrome sections 120 were plated using low current densitieson the order of 1 mA/17 mm². As the current density increases, even atlevels as low as 20 mA/17 mm², either internal stress was high, causingthe chrome to peel off, or severe pitting occurred. The geometry ofchrome sections 120 were determined by resist regions 116.

Next, and as shown schematically in FIG. 12, the remaining curedphotoresist, in resist regions 116, were removed using a basic solution.Finally, and as shown schematically in FIG. 13, the remaining copperlayer 112 was removed using a sodium persulfate bath as discussed above.The resulting patterned roll has opaque regions corresponding to nickel110 and chrome sections 120, and transparent regions corresponding towhere tie layer 104 is not covered by opaque material.

The disclosure should not be considered limited to the particularexamples described above, but rather should be understood to cover allaspects of the disclosure as set out in the attached claims. Variousmodifications, equivalent processes, as well as numerous structures towhich the disclosure can be applicable will be readily apparent to thoseof skill in the art upon review of the instant specification.

We claim:
 1. A method for patterning an opaque web having a first sideand a second side, the method comprising steps of: patterning a curablematerial onto a web having a first side and a second side with a firstpatterned roll and a second patterned roll, the first patterned rollcomprising a first plurality of raised opaque regions disposed on atransparent substrate and the second patterned roll comprising a secondplurality of raised opaque regions disposed on a transparent substrate;and directing ultraviolet radiation at least partially through the firstpatterned roll and second patterned roll, thereby curing the curablematerial on the first side of the web to form a first pattern and curingthe curable material on the second side of the web to form a secondpattern; wherein the first and second sides of the web are patternedwhile the web is in continuous motion such that the first and secondpatterns are maintained in continuous registration to within 100micrometers.
 2. The method of claim 1, wherein the first and secondpatterns are transferred to first and second sides of the web inregistration to within 10 micrometers.
 3. The method of claim 1, whereindisposing curable material onto the web comprises: disposing curablematerial onto the first patterned roll prior to the first side of theweb contacting the first patterned roll; and disposing curable materialonto the second patterned roll prior to the second side of the webcontacting the second patterned roll.